Related Field
The present invention relates to a centrifugal machine for solid materials with granular characteristics, which aggregates the function of carrying them in a reliable, safe and effective manner. Particularly, the present invention relates to a compact centrifugal machine of continuous flow, capable of removing liquids from granular solid materials, as well as of carrying the previously centrifuged materials in directions, distances and heights configured according to the demand for application, further preventing damages thereof, without impairing the efficacy of the centrifuging process.
Description of Related Art
Coffee beans are the type of granular solid material consisting of one of the main products of the world agribusiness. For this reason, one constantly looks for technique and solutions capable of reducing production costs and that, in addition, provides a final product of high quality and which meets the requirements for export.
In this regard, one of the main factors that influence the quality of coffee is the way of handling/treating it in the processing that follows harvest, chiefly at the drying step, which consists in evaporating the moisture present on the exposed surface of the coffee beans. It should be noted that coffee growing has post-harvest steps that cause the coffee beans to pass through a moist route initially.
Thus, drying is a quite important step in the process of treating coffee beans, in order to obtain a final product of high quality, since the ripe coffee beans are highly perishable due to the conditions of high moisture at harvest time. If the coffee beans are kept under conditions of high moisture for a given period of time, fungi begin to develop on the surface of the beans, which, coupled to the increase in respiration rate and temperature rise, will lead to fermentation. So, important characteristics of coffee such as aroma and taste deteriorate, that is, the quality of the final product is significantly affected.
Usually, the drying of coffee beans is carried out manually, in house yards, such as trodden-earth, cement or asphalt floor. However, this method is susceptible to weather variations, which may impair its efficacy, since at low temperatures and/or on a high level of moisture the dying time increases, causing damages to the coffee-growers. Besides, the drying on trodden-earth yards usually requires a relatively long time for carrying out the process and further requires large areas for building them. Additionally, it is also necessary to hire labor for conducting the drying process. Such factors contribute decisively to enriching the final product.
On the other hand, there are already a few techniques used for reducing the time it takes to remove water from the surface of the coffee beans, through automated machines such as mechanical dryers or similar equipment.
For instance, Brazilian patent application PI 0201900-0 describes a machine intended for removing excess water from the surface of the coffee beans by the principle of evaporation, by means of a forced hot-air stream capable of passing through the layer of grains that float on a perforated surface.
Another known automated solution for drying coffee beans is centrifugation, which consists of a technique based on the application of a centripetal force that is greater than gravity and can be increased by raising the rotation velocity. Centrifugation is a technique often used in the industries for separating solid from liquid, liquid from gaseous or still for separating two types of liquids.
For instance, Brazilian patent application PI 0304448-3 relates to a centrifuge capable of removing surface water and/or coffee-been wash water. Such a centrifuge comprises a drum with the shape of a horizontal truncated cone, constituted by a perforated metal plate, the rotation of which is controlled. This centrifuge has the limitation that it is not possible to control exactly the residence time of the product and centrifugation effect. Besides, the effectiveness of its functioning depends directly on the beans having good rolling characteristics, since they should roll inside the cone trunk until they reach the outlet without the aid of any specific device. Since the coffee beans not always have good rolling characteristic, there is a non-negligible chance of clogging the centrifugal machine, which restricts the use thereof to a limited range of granular materials, namely: those that have a rounded shape and greater rigidity.
Patent application PI 0502946-5 describes a centrifugal machine for coffee beans, provided with a vertical axle having a lower portion with an inlet for the coffee beans, which in turn are carried to an upper portion of the vertical axle by means of two endless screws that rotate in clockwise and counterclockwise direction. In addition, the centrifuge has a cylindrical sieve capable of permitting the liquid phase of the centrifuged material to come out, which involves the endless screws. Additionally, the centrifuge further comprises a cylinder that involves the cylindrical sieve to lead the liquid out of the machine. It should be noted that the rising flow of coffee beans in this machine is forced by the action of the endless screws from the bottom of the machine to its top, which generates an excess pressure on the coffee beans, resulting in a significant percentage of damaged grains. For this reason, it is recommended in the specification of this application that moderate rotation be adopted in order to balance the benefit of removing surface water with a lower percentage of damaged beans, which naturally impairs the efficacy of the machine.
Therefore, the presently known centrifugal machines are not capable of meeting satisfactorily all the requirements of coffee growing, so as to enable the replacement of manual methods that are sill often used at present. In other words, there is a demand for technologies that are capable of optimizing the process of drying coffee beans, in order to increase the production scale, while maintaining the quality of the product, coupled with a relatively low cost.